Electromagnetic emission from neutron star mergers has likely been observed for decades now in the form of SGRBs, and a first kilonova may have been observed in the afterglow of GRB130603B as early as 2013 [1]}, [2]}. However, our current understanding of the engine powering SGRBs is not sufficient to provide us with much information about the parameters of the binary system that created the burst – or even to differentiate between a BNS and NSBH merger. Gravitational wave observations provide more direct information about the properties of the compact objects. So far, two systems have been observed with component masses most easily explained by the merger of two neutron stars: GW170817 [3]} and GW1902425 [4]}. The former is a relatively low mass system, whose observation was followed by a weak SGRB (most likely observed off-axis), radio emission most likely associated with a relativistic jet, and a clear kilonova signal most easily explain by a combination of at least two outflow components – one that led to strong r-process nucleosynthesis, and one that did not. The exact process that produced these outflows remain a subject of research today. GW190425 has a higher total mass (\(3.4M_\odot \) ). There was no observed electromagnetic counterpart to that signal, a relatively unsurprising result considering the large uncertainty in the location of the source and the high likelihood that such a system did not eject a significant amount of matter [5]}, [6]}, [7]}, [8]}. At least two NSBH mergers were observed in 2020 [9]}, with more candidates also available in the latest gravitational wave catalogue [10]}. None of these systems was however expected to lead to the disruption of the neutron star, and thus their lack of electromagnetic counterpart was unsurprising.
